Dipping is superior to cusums analysis in assessment of the risk of stroke in a case-control study

Background: Blunted nocturnal decline in blood pressure (BP) is associated with increased risk of stroke. Mean day-night BP difference (dipping) and cusums-derived circadian alteration magnitude (CDCAM) of BP are the common measures of diurnal BP variation. Although a significant number of clinical trials have demonstrated that dipping is associated with a lower risk of cardiovascular events, the clinical value of CDCAM of BP is unknown. We evaluated the association between dipping and CD-CAM of BP and the risk of stroke. Methods: We analyzed 24-h ambulatory BP recordings of 110 control subjects and 91 stroke survivors enrolled in a case-control stroke study. Nondipping was defined as nocturnal drop of < 10 mm Hg in systolic BP. The associations between nondipping, CDCAM of BP, and risk of stroke were calculated in the same sample. Results: There were significantly fewer nondippers in the control group as compared with those among the stroke survivors. The odds ratio for stroke of nondippers was 2.3. By contrast, there was no significant difference in CDCAM of systolic BP between the control and stroke survivor groups. This finding could not be explained by the presence of reverse dippers in both groups. Conclusions: In this case-control study, classification of subjects into dippers and nondippers was found to be more clinically useful than cusums analysis of BP profile. Analysis of prospective data is needed to determine the clinical value of the cusums analysis of BP profile.